This invention is related to secured entrance door used for office or residence.
For security purpose, door chains and/or peeping hole are used for entrance door of office and residence. Such apparatus is expected that people take care for strangers before opening the door. However, when opening the door after recognizing that the stranger is harmless, the entrance has no protection at all.
If a malicious visitor pretends a postman who deliver postal parcels, or a money collector, eye hole or door chains is useless, because article transfer through half-closed door with door chains is very restricted and almost impossible. Ordinary people readily open the door when they recognize someone outside the door just wants to give a reasonable article and need a signature. This security defect of entrance door is based on the fact that a conventional door lacks safe article transfer function with preventing forced entry of human beings.